The retired supermodel is locked in a bitter divorce battle with publishing mogul Peter Brant as they attempt to thrash out the details of their separation and custody arrangements for their three children.
The split has turned ugly in recent months - they have both been ordered to undergo random drug testing at the other's request, while Seymour also accused her former partner of attaching a satellite tracking device to her car to monitor her movements.
She is now determined to involve the detective hired by Brant in the ongoing court proceedings, alleging the sleuth concocted "false allegations" against her in a bid to help her estranged husband.
Papers filed at Manhattan Supreme Court in New York City ask permission for Seymour's legal team to question the detective, an employee of 1st Class Investigations, at a deposition.
The request alleges the "surveillance was improper, entailed fabricated allegations (and) was calculated to harass and defame the petitioner. (We need to) test the veracity of any allegations to be used against her at trial."
The divorce hearing is scheduled to begin next month (Sep10).